Newer ext4 systems use delayed allocation to improve performance. This delays block allocation until it writes data to disk. Delayed allocation improves performance and reduces fragmentation by using the actual file size to improve block allocation.

This feature might increase the risk of data loss in cases where a system loses power before all of the data has been written to disk. This can occur if a program is replacing the contents of a file without forcing a write to the disk with fsync. To reduce this risk, make sure the default auto_da_alloc option is enabled on ext4 file systems.

The following changes can be made in the /etc/fstab file.